The present invention relates to a metal gasket, more particularly, a metal cylinder head gasket to be installed between a cylinder head and a cylinder block of the internal combustion engine.
Conventionally, as a cylinder head gasket to be installed between a cylinder head and a cylinder block, a metal gasket formed of one or a plurality of metal plates has been widely used.
In the conventional gasket, as a number of metal plates for constituting the gasket is reduced, it has been known and pointed out that a reduction of a sealing ability occurs due to a foreign material. Namely, when a gasket is installed between a cylinder head and a cylinder block, a foreign material, such as cutting chips of metals in forming the cylinder head and the cylinder block, may be interposed between the gasket and the cylinder head and/or between the gasket and the cylinder block. If the foreign material is not caught or deposited on a bead of the gasket, the sealing ability is not reduced. However, if the foreign material is deposited on the bead of the gasket, when the absorbing ability of the bead for the foreign material is small due to the reduction of the number of the metal plates for the gasket, the sealing ability of the gasket is affected or reduced.
The present invention has been made in view of the above, and an object of the invention is to provide a metal gasket, wherein even if a foreign material is disposed on a bead between a cylinder head and a cylinder block, a sealing ability at a bead of the gasket is not reduced by the foreign material.
Another object of the invention is to provide a metal gasket as stated above, wherein the gasket can be formed of one or a plurality of metal plates.
Further objects and advantages of the invention will be apparent from the following description of the invention.
A metal gasket for an internal combustion engine of the invention is formed of a first metal plate extending substantially throughout an entire area to be sealed. The first metal plate includes a first hole corresponding to a hole of the engine to be sealed, and a first bead projecting outwardly from the first metal plate to surround the first hole. The first bead has a concave formed inside the first bead and extends inwardly from an outer surface of the first metal plate. In the invention, a sealing material is disposed in the concave to project outwardly from the outer surface of the first metal plate.
In the gasket of the invention, the gasket is disposed such that the concave formed by the bead and having the sealing material therein faces the cylinder head or cylinder block where the foreign material is likely to adhere. In case the foreign material, such as metal chip, is not caught or deposited on the bead, the sealing ability of the bead or the gasket is not lowered at all.
Even if the foreign material is caught or deposited on the bead, the sealing ability of the bead or gasket is not lowered. In particular, in case the foreign material is oriented along the bead, the foreign material is pushed into the concave of the bead, so that the foreign material does not affect the sealing ability of the bead.
In case the foreign material is oriented across the bead, the foreign material is pushed between the cylinder head and the cylinder block when the gasket is installed. Thus, the foreign material is flattened and pushed into the sealing material to thereby be covered by the sealing material. Therefore, the reduction of the sealing ability in the gasket due to the foreign material is prevented.
As stated above, since the sealing material is disposed in the concave of the bead, even if a foreign material, such as metal chip, is held between the bead of the gasket and the cylinder head or cylinder block, the reduction of the sealing ability due to the foreign material deposited on the bead is prevented.
The sealing material may be a foamed sealing material or paint, which includes an inside portion disposed in the concave and an outside portion located outside the concave projecting outwardly from the outer surface of the metal plate. The outside portion of the sealing material has a length extending over the width of the concave in a width direction of the bead, which is equal to or less than 2 mm. Also, a ratio of the sealing material at the inside portion and the outside portion is 3:1 to 1:1.
The metal gasket may further include a second metal plate including a second hole corresponding to the first hole and a second bead projecting outwardly from the second metal plate to surround the second hole and having a concave formed inside the second bead. The sealing material is disposed in the concave to project outwardly from an outer surface of the second metal plate. The second metal plate is disposed on the first metal plate such that the sealing materials of the first and second metal plates face outwardly of the metal gasket to directly contact the cylinder head and the cylinder block.